There are various media via which data can be communicated including terrestrial and satellite radio frequency signals for both broadcast systems and cellular mobile communication systems where mobile terminals communicate using radio signals to a network of base stations. Another media for communicating data is a cable network which can be a coaxial cable or optical fibre in which data is modulated and communicated through the cable. Cable systems can be used to form broadcast systems in which a Cable Modem Termination System (CMTS) or head end modulates data onto signals for transmission through the cable network to a receiver which is known as a Cable Modem (CM). An example of a cable modem system which has been developed for communicating data including television signals via a cable network is the Data Over Cable Service Interface Specifications (DOCSIS) system which is administered by CableLabs. DOCSIS 3.0 for example provides a physical layer and a media access layer specification for arranging for data to be communicated via a cable network. The specification provides various communication techniques between the CMTS and the CMs for efficiently using an available bandwidth within the cable network.
One improvement which can be made to CMs is to reduce power consumption particularly for example when there is no payload data being transmitted to the CM by the CMTS.